水稻胚囊发育畸变的细胞学和遗传学研究

1．水稻多卵卵器的起源：被子植物的卵器中通常只有一个卵细胞。我们在水稻多胚品系胚囊中观察到二卵卵器和三卵卵器，本研究对其大孢子发生和胚囊发育进行了细胞胚胎学观察，揭示了水稻多卵卵器的起源．观察结果表明，该品系能进行正常的大孢子发生。大孢子母细胞进行正常的减数分裂形成四个大孢子靠近合点端的大孢子发育，其它三个退化。功能大孢子第一次有丝分裂后两个子核被一中央大液泡分隔在胚囊珠孔端和合点端，与此同时胚囊出现不均衡生长，珠孔端迅速膨大，合点端几乎不增大，致使二核末期的胚囊呈倒梨形．紧接着发生第二次有丝分裂，合点端核分裂时纺锤丝与胚囊纵轴平行，而珠孔端核分裂时纺锤丝与胚囊纵轴成4 5度夹角．由此产生的四核胚囊中，合点端一核向胚囊中部或中上部（胚囊珠孔端）迁移，四核胚囊再经一次有丝分裂形成两种类型的核分布偏离蓼型的八核胚囊。一种类型是珠孔端四个核，中部与合点各二个核，在胚囊细胞化过程中，珠孔端四核 分化成四细胞卵器，其中卵细胞和助细胞各二个，中部的二核分化成二极核中央细胞，合点 端的二核形成反足细胞。另一种类型是珠孔端六个核，合点端二个核，在胚囊细胞化过程中， 两端各一核向中部迁移分化成二极核中央细胞，珠孔端剩余的五核分化成五细胞卵器，其 中卵细胞三个，助细胞二个，合点端的一核迅速分裂形成反足细胞． 2．水稻同源三倍体TAR的生殖特性：TAR的单穗结实率平均可达10%，核型分析表明此三倍体产生的后代个体仍为具有36条染色体的三倍体．细胞胚胎学初步观察显示TAR为一具兼性无融合生殖特性的水稻新种质，其胚珠几乎都能进行胚囊的分化，但其中仅有33%的胚囊有较正常的结构，9%的胚囊在散粉前进行胚胎发生，58%的胚囊发育显著异常，表现为极性紊乱、多极核或缺失雌性生殖单位等。 3．水稻亚种间杂种败育的细胞学基础：对普通栽培稻不同品种类型间杂种颖花败育的细胞学基础及雌性败育的过程进行的细胞学研究表明：1）引起杂种颖花败育的原因有胚囊败育，花粉败育、开花时花药不开裂和雌雄异熟．其中胚囊败育而丧失受精能力是引起低结实率的最重要的因素，开花时花药不开裂和雌雄异熟在一定程度上形成了雌雄性细胞时间和空间的隔离屏障。2）杂种植株的所有大孢子母细胞都能进行正常的减数分裂形成四个大孢子，败育主要发生在靠近合点端的功能大孢子分化形成胚囊的早期，有的胚囊母细胞在进行第一次有丝分裂前便萎缩解体，多数能完成一次或二次有丝分裂形成二核或四核败育胚囊．败育的共同特征是无液泡的分化，细胞质少或退化，在败育胚囊残迹部位，解体的珠心细胞和萎缩的胚囊残溃混杂垛叠．已受精的杂种子房没有观察到胚及胚乳发育的异常．籼粳杂种胚囊败育频率较高． 4．籼粳杂种生殖障碍的基因定位：应用具有1 37个标记位点的籼粳杂交窄叶青8号/京系17)F1花药培养获得的127个双单倍体OH）群体构建的R FLP图谱，对控制籼粳杂种颖花败育的基因座位进行了定位研究。结果在第1、3、4、5、6、7、8、1 2染色体上检测到1 0个基因座位，其中第3、12染色体上的2个不育基因位点str3和str12与同一杂交组合F2分离群体中发现的异常分离热点处于相同的染色体区段．stj-6的基因加性效应为负值，有增加籼粳亲和性的作用;其余的不育基因座位皆有增加籼梗杂种不育性的作用． 5．籼粳杂种胚囊败育的遗传分析和基因定位：利用DH系构建的分子图谱及DH系衍生的2个回交群体定位了引起籼梗杂种胚囊败育的2个互补的主效基因esa-l（E1或e1位点）和esa-2（E2或e2位点），它们分别位于第6和第1 2染色体．在不育基因位点，籼稻基因型为EIEle2e2，粳稻基因型为elelE 2E 2，杂交后代中基因型为EIE2，Ele2、elE 2的雌配子体正常发育，携带ele2基因型的雌配子体表现败育．胚囊育性受配子体基因型控制，孢予体遗传背景影响胚囊败育基因的表达.

A high throughput Nile red method for quantitative measurement of neutral lipids in microalgae

Isolation of high neutral lipid-containing microalgae is key to the commercial success of microalgae-based biofuel production. The Nile red fluorescence method has been successfully applied to the determination of lipids in certain microalgae, but has been unsuccessful in many others, particularly those with thick, rigid cell walls that prevent the penetration of the fluorescence dye. The conventional "one sample at a time" method was also time-consuming. In this study, the solvent dimethyl sulfoxide (DMSO) was introduced to microalgal samples as the stain carrier at an elevated temperature. The cellular neutral lipids were determined and quantified using a 96-well plate on a fluorescence spectrophotometer with an excitation wavelength of 530 nm and an emission wavelength of 575 run. An optimized procedure yielded a high correlation coefficient (R-2 = 0.998) with the lipid standard triolein and repeated measurements of replicates. Application of the improved method to several green algal strains gave very reproducible results with relative standard errors of 8.5%, 3.9% and 8.6%, 4.5% for repeatability and reproducibility at two concentration levels (2.0 mu g/mL and 20 mu g/mL), respectively. Moreover, the detection and quantification limits of the improved Nile red staining method were 0.8 mu g/mL and 2.0 mu g/mL for the neutral lipid standard triolein, respectively. The modified method and a conventional gravimetric determination method provided similar results on replicate samples. The 96-well plate-based Nile red method can be used as a high throughput technique for rapid screening of a broader spectrum of naturally-occurring and genetically-modified algal strains and mutants for high neutral lipid/oil production. (C) 2009 Published by Elsevier B.V.

Surface characterization study on SnO2 powder modified by thiourea

The SnO2 material prepared by sol-gel method was modified by thiourea solution in different concentrations (0.05, 0.1 and 0.2 mol dm(-3)). Then the structure and the average grain size of the SnO2 material were investigated by X-ray power diffraction. In order to understand the nature of the species on the SnO2 surfaces, the thermal gravimetric and differential thermal analyzer (TG-DTA) and IR spectra of these modified and unmodified sample were taken. The result indicates that the stability of oxygen adsorbed on thiourea-modified surface was improved and the amount of surface hydroxyl groups adsorbed on this grain surface was decreased. The thiourea adsorbed on SnO2 grain surface is translated to SO42- after sintered at 600 degrees C. SO42- species stabilize the resistance of the SnO2 sensor. (c) 2005 Elsevier B.V. All rights reserved.

Design and operation of integrated pilot-scale dimethyl ether synthesis system via pyrolysis/gasification of corncob

The integrated pilot-scale dimethyl ether (DME) synthesis system from corncob was demonstrated for modernizing utilization of biomass residues. The raw bio-syngas was obtained by the pyrolyzer/gasifier at the yield rate of 40-45 Nm(3)/h. The content of tar in the raw bio-syngas was decreased to less than 20 mg/Nm(3) by high temperature gasification of the pyrolysates under O-2-rich air. More than 70% CO2 in the raw bio-syngas was removed by pressure-swing adsorption unit (PSA). The bio-syngas (H-2/CO approximate to 1) was catalytically converted to DME in the fixed-bed tubular reactor directly over Cu/Zn/Al/HZSM-5 catalysts. CO conversion and space-time yield of DME were in the range of 82.0-73.6% and 124.3-203.8 kg/m(cat)(3)/h, respectively, with a similar DME selectivity when gas hourly space velocity (GHSV, volumetric flow rate of syngas at STP divided by the volume of catalyst) increased from 650 h(-1) to 1500 h(-1) at 260 degrees C and 4.3 MPa. And the selectivity to methanol and C-2(+) products was less than 0.65% under typical synthesis condition. The thermal energy conversion efficiency was ca. 32.0% and about 16.4% carbon in dried corncob was essentially converted to DME with the production cost of ca. (sic) 3737/ton DME. Cu (111) was assumed to be the active phase for DME synthesis, confirmed by X-ray diffraction (XRD) characterization.

Scale study of direct synthesis of dimethyl ether from biomass synthesis gas

We investigated the synthesis of dimethyl ether (DME) from biomass synthesis gas using a kind of hybrid catalyst consisting of methanol and HZSM-5 zeolite in a fixed-bed reactor in a 100 ton/year pilot plant. The biomass synthesis gas was produced by oxygen-rich gasification of corn core in a two-stage fixed bed. The results showed that CO conversions reached 82.00% and 73.55%, the selectivities for DME were 73.95% and 69.73%, and the space-time yields were 124.28 kg m- 3 h- 1 and 203.80 kg m- 3 h- 1 when gas hourly space velocities were 650 h- 1 and 1200 h- 1, respectively. Deoxidation and tar removal from biomass synthesis gas was critical to the stable operation of the DME synthesis system. Using single-pass synthesis, the H2/CO ratio improved from 0.98-1.17 to 2.12-2.22. The yield of DME would be increased greatly if the exhaust was reused after removal of the CO2.

Effects of metal catalysts on CO2 gasification reactivity of biomass char

The effects of five metal catalysts (K, Na, Ca, Mg, and Fe) on CO2 gasification reactivity of fir char were studied using thermal gravimetric analysis. The degree of carbonization, crystal structure and morphology of char samples was characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The CO2 gasification reactivity of fir char was improved through the addition of metal catalysts, in the order K>Na>Ca>Fe>Mg. XRD analysis indicated that Na and Ca improved the formation of crystal structure, and that Mg enhanced the degree of carbon structure ordering. SEM analysis showed that spotted activation centers were distributed on the surface of char samples impregnated with catalysts. Moreover, a loose flake structure was observed on the surface of both K-char and Na-char. Finally, the kinetic parameters of CO2 gasification of char samples were calculated mathematically.

Partial oxidation reforming of biomass fuel gas over nickel-based monolithic catalyst with naphthalene as model compound

With naphthalene as biomass tar model compound, partial oxidation reforming (with addition of O-2) and dry reforming of biomass fuel gas were investigated over nickel-based monoliths at the same conditions. The results showed that both processes had excellent performance in upgrading biomass raw fuel gas. Above 99% of naphthalene was converted into synthesis gases (H-2+CO). About 2.8 wt% of coke deposition was detected on the catalyst surface for dry reforming process at 750 degrees C during 108 h lifetime test. However, no Coke deposition was detected for partial oxidation reforming process, which indicated that addition of O-2 can effectively prohibit the coke formation. O-2 Can also increase the CH4 conversion and H-2/CO ratio of the producer gas. The average conversion of CH4 in dry and partial oxidation reforming process was 92% and 95%, respectively. The average H-2/CO ratio increased from 0.95 to 1.1 with the addition of O-2, which was suitable to be used as synthesis gas for dimethyl ether (DME) synthesis.

Bio-syngas production from biomass catalytic gasification

A promising application for biomass is liquid fuel synthesis, such as methanol or dimethyl ether (DME). Previous studies have studied syngas production from biomass-derived char, oil and gas. This study intends to explore the technology of syngas production from direct biomass gasification, which may be more economically viable. The ratio of H-2/CO is an important factor that affects the performance of this process. In this study, the characteristics of biomass gasification gas, such as H-2/CO and tar yield, as well as its potential for liquid fuel synthesis is explored. A fluidized bed gasifier and a downstream fixed bed are employed as the reactors. Two kinds of catalysts: dolomite and nickel based catalyst are applied, and they are used in the fluidized bed and fixed bed, respectively. The gasifying agent used is an air-steam mixture. The main variables studied are temperature and weight hourly space velocity in the fixed bed reactor. Over the ranges of operating conditions examined, the maximum H-2 content reaches 52.47 vol%, while the ratio of H-2/CO varies between 1.87 and 4.45. The results indicate that an appropriate temperature (750 degrees C for the current study) and more catalyst are favorable for getting a higher H-2/CO ratio. Using a simple first order kinetic model for the overall tar removal reaction, the apparent activation energies and pre-exponential factors are obtained for nickel based catalysts. The results indicate that biomass gasification gas has great potential for liquid fuel synthesis after further processing.